Moisture build-up/Heater HELP PLEASE!!!

[ryans69chevy]

Does anyone know what could be causing the windows on the inside to fog up and then freeze after the heater is started?

It's very dangerous to drive when this happens...steering with one hand while scraping the windows with the other. I'm not really sure what is causing this...I thought it was my weatherstripping on the doors so I replaced it with a temporary weatherstrip. This fixed one of the problems which was the windows were freezing on the inside before I was even in the pickup. But now it's freezing all the windows when I turn on the heater. Has anyone ever had this happen or know how to fix it?

I'm thinking maybe it could have something to do with the heater core box under the hood. Since I pop my hood slightly to get an extension chord in there to plug my lower radiator heater hose in. I don't know if this is normal to have a heater core box that is in two pieces and that don't connect all the way like a 1/4" gap maybe snow gets in there and melts which causes moisture to flow through the defroster hoses? I'm going to put a piece of duct tape over the gap today. Or could it have something to do with my antifreeze mixture? I drove this truck all last winter and don't remember the inside of the windows freezing up....

Thanks for any advice